When drawing a "map" of a circuit it is not practical to try to completely
label each part; instead, a standardized set of visual representations for the
electrical components has been established. These are called Schematic
Symbols, and the "map" of a
circuit is also referred to as a schematic.

Component 2 in figure T1 is a transistor. A transistor is a control element
and has three terminals. The one on the left is called the base. It is the
control input and is similar to pushing the gas pedal on your car; the little
amount of power your foot puts into pushing the pedal creates a larger amount
of power to come from the engine. The upper right terminal is the collector
and has current flowing into it in porportion to the current into the base
multiplied by the gain of the transistor (also called hfe or beta). The lower
right terminal has an arrow that indicates the direction the current will flow
from both the base and the collector.

Component 3 in figure T-1 is an incandescent lamp. The small looping line inside
the border shape represents the filament inside the lamp. Current flowing
through the circuit causes the filament to glow and emit light.

Component 4 in figure T1 is a Battery. This is the energy source to power the
lamp when a voltage is applied to the input of the circuit. The symbol has one
or more sections indicating a number of cells (piles) in the battery pack. The
longer line represents the positive terminal while the shorter line is the
negative terminal.

A capacitor consists of two conductors (wires, plates, etc) separated by an
insulator (such as air). If you look at figure T2 you will see that a
capacitor has the symbol of two lines (one usually curved to indicate which
side it is) with a gap between. Each line represents a conductor and the gap
represents the insulator.

The black arrow with a line across the tip (like component 5) is the schematic
for a diode; a Light Emitting Diode has essentially the same characteristics
of a diode except that it also emits light, therefore the schematic symbol
looks like a diode with little zigzag arrows coming out to represent the light
waves emanating from the diode.

A Variable Resistor is easily identified because it looks like a normal
resistor (a jagged zig-zag line with straight lines entering and leaving) but
with an additional arrow pointing at the middle of the zig-zag perpendicular
to the rest of the component symbol. This arrow represents the brush or
connection on the variable resistor (potentiometer) that moves when you adjust
the resistance.

In the schematic symbol, the two ends have a total resistance between them of
the total value of the resistor and the resistance between each end and the
middle arrow varies.

A transformer consists of two inductively coupled coils that are not directly
connected together. If you look at the symbol you can see the representation
of a coil on each side with two lines in the middle to indicate the
separation.

The antenna schematic symbol looks a little like the stereotypical "satellite
dish"; it's a triangle with one of the points connected to the circuit and the
opposite side not connected to anything and a line through the middle. It is
usually not hard to remember because it legitimately looks like an antenna =]

Which of the following is accurately represented in electrical schematics?

A.

Wire lengths

B.

Physical appearance of components

C.

The way components are interconnected

D.

All of these choices are correct

T6C13

An electrical circuit schematic is like a blueprint for an electrical system;
another good analogy is a street map. the street map may not show all the
trees, elevations, etc, but it does show what streets are connected together
and where. Similarly an electrical circuit schematic diagram shows how all the
components connect to each other and thus how the circuit works.

A schematic diagram does not show you where the circuits are physically
located or what they look like, nor how far apart they are.